In recent years, novel pigments, dyes and the like have been actively developed in order to provide them with high added values or improved properties. Dyes are color materials having affinities for fibers, i.e., color materials having dyeing abilities, and therefore they are required to have solubility somehow or other. In that context, water-soluble azo compounds have been developed as azo dyes. As specific examples of such water-soluble azo compounds, those prepared from 2-hydroxynaphthalene-6-carboxylic acid (see, for example, the Japanese Patent Publication (Kokai) Nos. H1-215862 (1989) and H1-245060 (1989)) are known.